1. Field of the Invention
The present invention relates to a mobile packet communication system that supports data communications, including Internet communications, in a high-speed mobile communication system such as a cellular communication network. Currently, studies on next generation mobile communication systems are proceeding in research institutes, standards bodies, and other organizations in various countries of the world, aiming to provide multimedia communication services, including high-speed data communications up to 2 Mbps, in the next generation of mobile communication systems.
Among others, packet communication services, including the Internet, are expected to displace the current mobile communication services intended primarily for voice communication and to become the core communication service in the next generation of mobile communication systems. Furthermore, studies have begun on communication networks that integrate mobile terminals connected to mobile radio communication networks and fixed equipment including Internet service providers (ISPs) and LANs within user premises.
2. Description of the Related Art
FIG. 20 is a diagram showing the configuration of a prior art mobile packet communication system in a cellular communication network. The mobile packet communication system comprises mobile terminals 20-1-1 to 20-1-2, subscriber nodes 20-2-1 to 20-2-3, gate nodes 20-3-1 to 20-3-2, and location registration servers 20-4-1 to 20-4-3, and is connected via the gate nodes 20-3-1 to 20-3-2 to fixed equipment 20-5-1 to 20-5-2, such as an Internet service provider (ISP) or a local area network (LAN) within user premises, connected to a fixed network.
The location registration servers 20-4-1 to 20-4-3 are provided, one for each group of terminal numbers (for example, E.164 addresses) having the same high-order digits and assigned to the mobile terminals 20-1-1 to 20-1-2, and each of the location registration servers 20-4-1 to 20-4-3 includes a location register 20-6. E.164 is the international standard telephone numbering (terminal addressing) scheme defined by the ITU-T.
The location register 20-6 stores for each of the mobile terminals 20-1-1 to 20-1-2 the address [ADR6 -8] of its current location (the subscriber node, 20-2-1 to 20-2-3, currently serving the mobile terminal) and the address [ADR4-5] of the gate node, 20-3-1 to 20-3-2, connected to the user LAN or the ISP to which the mobile terminal, 20-1-1 to 20-1-2, subscribes.
The subscriber nodes 20-2-1 to 20-2-3 and the gate nodes 20-3-1 to 20-3-2 each include a server search table 20-7 which is used to search for the addresses [ADR1 to ADR3] of the location registration servers 20-4-1 to 20-4-3 by reference to the high-order digits of the numbers of the mobile terminals 20-1-1 to 20-1-2.
Each of the gate nodes 20-3-1 to 20-3-2 further includes an address translation table 20-8 which is used to translate the address (IP address) contained in the header of a packet arriving from an external ISP or LAN into the number of a corresponding one of the mobile terminals 20-1-1 to 20-1-2.
FIG. 21 is a diagram for explaining the location registration operation for a moving mobile terminal in the prior art mobile packet communication system. In the figure, the configuration of the mobile packet communication system is the same as that shown in FIG. 20, and the same elements are designated by the same reference numerals. The location registration is performed in accordance with the following procedure consisting of steps (1) to (4)
(1) As the mobile terminal 20-1-1 moves into a new radio zone, it sends a location registration request to the subscriber node 20-2-1 in the new radio zone.
(2) Upon receiving the location registration request message from the mobile terminal 20-1-1, the subscriber node 20-2-1 searches the server search table 20-7 by reference to the high-order digit part [020] of the number [020-xxx1] of the mobile terminal 20-1-1, and retrieves the address [ADR1] of the corresponding location registration server.
(3) Location registration information (the address [ADR6] of the subscriber node 20-2-1) is transferred to the corresponding location registration server 20-4-1.
(4) The location registration server 20-4-1 updates the location register 20-6 based on the received location registration information.
FIG. 22 is a diagram for explaining the operation for packet transfer from the fixed equipment 20-5-2, such as an ISP or a user LAN, to the mobile terminal 20-1-1. In the figure, the configuration of the mobile packet communication system is the same as that shown in FIG. 20, and the same elements are designated by the same reference numerals. The packet transfer operation is performed in accordance with the following procedure consisting of steps (1) to (8).
(1) A packet containing the destination address [1.1.1] arrives at the gate node 20-3-2 from the fixed equipment 20-5-2 such as an ISP or a user LAN.
(2) The gate node 20-3-2 obtains the mobile terminal number [020-xxx1] from the destination address [1.1.1] by looking it up in the address translation table 20-8.
(3) Further, the gate node 20-3-2 searches the server search table 20-7 by reference to the mobile terminal number [020-xxx1] obtained in the above step, and retrieves the address [ADR1] of the corresponding location registration server 20-4-1.
(4) The gate node 20-3-2 requests the location registration server 20-4-1 of the address [ADR1] to send the location information concerning the designated mobile terminal.
(5) In response to the request, the location registration server 20-4-1 searches the location register 20-6 by reference to the number [020-xxx1] of the designated mobile terminal, and
(6) returns the location information (subscriber node address=[ADR6]) concerning the designated mobile terminal to the gate node 20-3-2.
(7) The gate node 20-3-2 that received the location information appends the mobile terminal location information (subscriber node address=[ADR6]) to the packet received from the fixed equipment 20-5-2, and transfers the packet to the subscriber node 20-2-1.
(8) The subscriber node 20-2-1 designated by the subscriber node address=[ADR6] receives the packet, and transfers the packet to the destination mobile terminal 20-1-1 after removing the location information (subscriber node address) from the packet.
FIG. 23 is a diagram for explaining the operation for packet transfer from the mobile terminal 20-1-2 to the fixed equipment 20-5-1 such as an ISP or a user LAN. In the figure, the configuration of the mobile packet communication system is the same as that shown in FIG. 20, and the same elements are designated by the same reference numerals. The packet transfer operation is performed in accordance with the following procedure consisting of steps (1) to (7).
(1) The mobile terminal 20-1-2 sends a communication start request to the subscriber node 20-2-3.
(2) The subscriber node 20-2-3 that received the communication start request searches the server search table 20-7 by reference to the number [020-xxx2] of the mobile terminal that issued the communication start request, and retrieves the address [ADR1] of the corresponding location registration server.
(3) The subscriber node 20-2-3 requests the location registration server 20-4-1 of the address [ADR1] to send the address of the gate node, 20-3-1 to 20-3-2, connected to the user LAN or the ISP to which the originating mobile terminal 20-1-2 subscribes.
(4) In response to the request, the location registration server 20-4-1 retrieves the address [ADR4] of the corresponding gate node from the location register 20-6 by reference to the mobile terminal number [020-xxx2], and
(5) returns the address [ADR4] of the corresponding gate node to the subscriber node 20-2-3.
(6) The subscriber node 20-2-3 that received the address [ADR4] of the corresponding gate node appends the address [ADR4] of the gate node 20-3-1 to the packet data received from the mobile terminal 20-1-2, and transfers the packet to the gate node 20-3-1.
(7) The gate node 20-3-1 designated by the gate node address=[ADR4] receives the packet, and transfers the packet to the fixed equipment 20-5-1 after removing the gate node address.
FIG. 24 is a diagram for explaining communication routes between the prior art mobile packet system and fixed equipment. Part (a) of the figure shows the packet communication routes from the mobile terminal to the fixed equipment, and part (b) shows the packet communication routes from the fixed equipment to the mobile terminal.
As shown in part (a) of the figure, all packets A, B, and C sent out from the mobile terminal 24-1 are routed through the mobile packet network 24-2, and are transferred together to the packet network (ISP/user LAN) in the fixed network 24-4, always passing through the gate node 24-3 predetermined for each mobile terminal. In the fixed network 24-4, the packets are individually routed and delivered to the respective destination processes such as a fixed terminal, FTP (File Transfer Protocol), WWW (World Wide Web), etc.
Likewise, as shown in part (b) of the figure, packets A, B, and C directed from the fixed network 24-4 to the mobile terminal 24-1 are delivered to the destination mobile terminal 24-1, always passing through the gate node 24-3 predetermined for each mobile terminal.
The prior art mobile packet communication system provides an access line between a mobile terminal and a specific ISP, user LAN, etc. in a fixed network, but the presence of a fixed network for routing individual packets is a prerequisite for the deployment of the system.
Accordingly, (1) there arises the problem that a common platform for integrating a mobile communication network and a fixed network cannot be constructed. At the present, it is common practice to construct the platforms separately, because of regulations that prohibit mobile communication service carriers operating fixed communication services and fixed communication service carriers operating mobile communication services, but in the future such regulations may be abolished.
In that case, a carrier wishing to support both mobile communication and fixed communication services would have to provide two platforms, one for the mobile communication service and the other for the fixed communication service, which would make administration operations complex and could pose a barrier to reducing the communication service costs.
Furthermore, (2) since communications must always be routed via a specified gate node between the mobile communication network and the fixed network, as earlier described, there can occur cases where the communication path has to be routed the long way around when the other party is actually located nearby, as shown in FIG. 25.
FIG. 25 is a diagram for explaining a roundabout communication route between the prior art mobile packet system and the fixed network. Part (a) of the figure shows a roundabout communication route for packet transfer from a mobile terminal to the fixed network, and part (b) shows a roundabout communication route for packet transfer between mobile terminals.
As shown in part (a) of FIG. 25, when a mobile terminal 25-1-1 located, for example, in Yokohama, sends out packets A, B, and C destined for destination processes, such as a fixed terminal, FTP, WWW, etc., located, for example, in Tokyo, Yokohama, and Kawasaki, via the mobile packet network 25-2 and fixed network 25-4, if the gate node 25-3 is, for example, in Osaka, the packets A, B, and C are always transferred through the gate node 25-3 in Osaka.
On the other hand, consider the situation where the mobile terminal 25-1-1 located, for example, in Yokohama sends out packets A, B, and C destined for another mobile terminal 25-1-2 also located in Yokohama, as shown in part (b) of FIG. 25; in this case also, the packets A, B, and C are transferred through the gate node 25-3 in Osaka.
This not only increases packet transfer delay time and degrades the quality of communication service, but also increases network traffic loads and adversely affects the quality of other communications.
Currently, the European Telecommunications Standard Institute (ETSI) is working toward the standardization of a mobile packet communication system (GPRS), but the basic system configuration is the same as that described above and, therefore, involves similar problems.
On the other hand, the Mobile-IP based mobile packet communication system that the Internet Engineering Task Force (IETF), the Internet standards board, has been studying is known as a mechanism that will support mobile communication services with minimum changes to the existing Internet mechanism.
FIG. 26 is a diagram for explaining the Mobile-IP based mobile packet communication system. In the Internet, a domain is defined for each geographically closed area (for example, within an office). An IP packet is routed to the domain based on its IP address, and from there, the packet is delivered to the end terminal based on a link layer address such as a MAC (Media Access Control) address on an Ethernet bus.
In Mobile-IP, a home agent HA 26-1 and a foreign agent FA 26-2 are defined for each domain. It is assumed that each terminal is usually located within a specific domain (home network).
When a mobile terminal MN (Mobile Node) of address [2.2] moves into another domain (visited network), the visited network transmits via its foreign agent FA the IP address (care-of address: in this example, [3.1]) of the foreign agent FA residing in the visited network to the home agent HA residing in the home network.
Any packet destined for the mobile terminal MN of address [2.2] is first intercepted by the home agent HA in the home network. The home agent HA appends the IP address [3.1] of the foreign agent residing in the network in which the mobile terminal MN is currently located, and the packet is encapsulated for transmission to the visited network. This eliminates the need for IP address allocation for the mobile terminal MN.
The foreign agent FA decapsulates the packet by removing the appended IP address of the foreign agent FA, and delivers the packet to the mobile terminal MN based on the link layer address (MAC address, etc.). On the other hand, any packet sent out from the mobile terminal MN is transferred directly from the visited network in accordance with the usual Internet rules.
Since Mobile-IP is based on Internet communications in existing fixed networks, as earlier noted, it is possible to integrate mobile communication networks with fixed networks. However, since communications are always routed via the home network, the previously described problem (2) remains to be solved.
Furthermore, though details will not be described here, Mobile-IP involves the widely recognized problem that it cannot be extended to high-speed mobile applications such as portable telephone systems, because it does not take account of high-speed mobility in the first place.
As described, with the prior art mobile packet communication system, it has not been possible to construct a common platform integrating packet transfers between a mobile terminal and fixed equipment while providing the capability to select an optimum route.